Method and apparatus for operating vacuum cleaner

ABSTRACT

Method and apparatus for operating a vacuum cleaner in which by detecting a rotational speed of a variable speed fan motor adapted to give a suction force to the cleaner and its change range, the choking state of the filter and the state of the cleaned surface are discriminated, and a speed command of the fan motor is corrected on the basis of the result of the discrimination, and the comfortable cleaning can be performed by the optimum suction force.

This is a divisional of application Ser. No. 07/365,491, filed June 13,1989, now U.S. Pat. No. 4,983,895, which in turn is a divisional ofapplication Ser. No. 07/105,598, filed Oct. 8, 1987, now U.S. Pat. No.4,880,474.

BACKGROUND OF THE INVENTION

The present invention relates to a vacuum cleaner and, moreparticularly, to a method and an apparatus for operating a vacuumcleaner in an in the optimum condition in accordance with the state ofthe cleaning surface and the choking state of the cleaner.

In vacuum cleaners, the suction is set to a constant value irrespectiveof the state of the cleaning surface. Therefore, the suction force iseither too strong or too weak for the cleaning surface or an object tobe cleaned, so that the optimum control which is comfortable to the usercannot be performed.

To solve this problem, such an optimum control can be realized by, forexample, controlling the motor of the cleaner to adjust the suction inaccordance with the cleaning surface. As a method of adjusting thesuction force of the cleaner, a method whereby the rotational speed ofthe drive motor is variably set is first considered. As ways of changingthe rotational speed of the motor, there have been known a method inwhich the phase is controlled using a thyristor and a method in whichthe rotational speed is controlled by an inverter.

A vacuum cleaner disclosed in the published application JP-A-60-242827relates to the latter method. Namely, this cleaner uses a brushlessmotor which is driven by an inverter.

Although the motor which is driven by the inverter is disclosed in theforegoing published application, nothing is taught with respect to thetechnical concept of allowing the motor to be automatically operated inan optimum condition in accordance with the state of the cleaningsurface or the choking state of the filter. In addition, means forimplementing this technical concept is not disclosed or suggested.

SUMMARY OF THE INVENTION

It is first object of the present invention to provide a method and anapparatus for operating a vacuum cleaner in which the suction force iscontrolled to provide an optimum condition in accordance with the stateof the cleaning surface and the choking state of the filter.

A second object of the invention is to provide an apparatus foroperating a vacuum cleaner in which the rotational speed of a brushlessDC motor is controlled to an optimum condition in accordance with theload state of the vacuum cleaner.

A third object of the invention is to provide an apparatus for operatinga vacuum cleaner in which one type of speed control unit and a motor canbe used for two kinds of voltage systems.

It is a first feature of the present invention that, in a vacuum cleanerhaving a filter to collect dust and a variable speed fan motor adaptedto produce a suction force for the cleaner, the rotational speed of thefan motor is sequentially detected at short periods during the cleaning,the state of the cleaning surface or an object to be cleaned is presumedfrom a fluctuation mode based on a change in rotational speed which wasdetected within a predetermined sampling time, and then the input of thefan motor is automatically adjusted to set the rotational speed of themotor to a speed which is suitable for the presumed state of thecleaning surface or the like.

It is a second feature of the invention that in a vacuum cleaner whichcomprises a brushless DC motor used as a drive source and a speedcontrol unit consisting of an inverter control unit to drive this motor,a control circuit of the inverter control unit comprises amicrocomputer, a current detecting circuit, a magnetic pole positiondetecting circuit, and a speed command circuit, and the load state ofthe cleaner is calculated by the microcomputer from a load current and arotational speed of the brushless DC motor, and a voltage or a currentwhich is applied to the brushless DC motor is controlled on the basis ofthe result of the load state so that the brushless DC motor has serieswound characteristic.

It is a third feature of the invention that, in a speed control unit ofa motor comprising a step-up chopper circuit to step up a voltage whichis obtained by rectifying an AC power source voltage, an electric powerconverter to control a current supplying angle (i.e. conducting periodof an angle) of an output voltage of the step-up chopper circuit whichis applied to a motor, and a control circuit to control the step-upchopper circuit and the electric power converter, the control circuithas: a power source voltage detecting circuit to detect the magnitude ofan AC power source voltage; and a speed control circuit for controllingthe speed of the motor by changing the output voltage of the step-upchopper circuit in a state in which the current supplying angle of theelectric power converter is held to a predetermined value in the casewhere the AC power source voltage is of a low voltage system, and forcontrolling the speed of the motor by changing the current supplyingangle of the electric power converter in the state in which the outputvoltage of the step-up chopper circuit is held to a predetermined valuein the case where the AC power source voltage is of a high voltagesystem.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vacuum cleaner according to anembodiment of the present invention;

FIG. 2 is a schematic block diagram of a speed control unit comprising abrushless DC motor and an inverter control unit;

FIG. 3 is a diagram showing performance curves of the vacuum cleaner;

FIGS. 4A and 4B are diagrams showing fluctuations in rotational speeddue to the choking state of a filter;

FIG. 5 is a diagram showing a fluctuation in rotational speed in thecase where the cleaning surface and the choking state of the filter areconsidered;

FIG. 6 is a diagram showing different fluctuation modes in rotationalspeed for different cleaning surfaces;

FIG. 7 is a diagram showing a function table in accordance with thecleaning surface;

FIG. 8 is a diagram showing the processing which is executed by amicrocomputer;

FIG. 9 is a control block diagram of an apparatus to drive the vacuumcleaner showing an embodiment of the invention;

FIG. 10 is a diagram showing performance curves in dependence on thepresence or absence of choking of the filter;

FIG. 11 is a diagram showing performance curves for various cleaningsurfaces;

FIG. 12 is a control block diagram showing another embodiment of thepresent invention;

FIG. 13 is a schematic diagram of a speed control unit showing anotherembodiment of the invention;

FIG. 14 is a diagram showing the processing operation of themicrocomputer;

FIG. 15 is a diagram showing performance curves of the vacuum cleaner;

FIG. 16 is a schematic block diagram showing a control circuit of aspeed control unit;

FIG. 17 is a schematic diagram of a speed control unit consisting of abrushless DC motor and an inverter control unit;

FIG. 18 is a diagram showing performance curves of a vacuum cleaner;

FIG. 19 is a schematic block diagram showing a control circuit of aspeed control unit;

FIG. 20 is a diagram showing performance curves of a vacuum cleaner;

FIG. 21 is a schematic block diagram showing a control circuit of aspeed control unit;

FIG. 22 is a diagram showing a speed control unit consisting of abrushless DC motor and an inverter control unit;

FIG. 23 is a diagram showing performance curves of a vacuum cleaner;

FIG. 24 is a diagram showing performance curves of a vacuum cleaner;

FIG. 25 is a diagram showing performance curves of a vacuum cleanerhaving a power saving function;

FIG. 26 is a schematic block diagram showing a control circuit;

FIG. 27 is an explanatory diagram showing the processing operation of amicrocomputer;

FIG. 28 is a diagram showing performance curves of a vacuum cleaner;

FIGS. 29A and 29B are diagrams showing changes in current to the statein which foreign matter is inhaled into an intake air passage and to thechoking state of a filter;

FIG. 30 is a schematic block diagram showing a control circuit to drivea brushless DC motor;

FIG. 31 is a block diagram showing a circuit constitution of the controlcircuit;

FIG. 32 is a diagram showing waveforms of an AC power source voltage anda power source current;

FIG. 33 is a characteristic diagram of an initial charging voltage of acapacitor;

FIG. 34 is a flowchart for a switching process of a speed control of amicrocomputer;

FIG. 35 is a characteristic diagram of a DC voltage to a speed commandvalue;

FIGS. 36A and 36B are diagrams showing waveforms of voltages which areapplied to a motor when its rotational speed is controlled by a step-upchopper circuit to improve the power factor;

FIGS. 37A and 37B are diagrams showing waveforms of voltages which areapplied to the motor when its rotational speed is controlled by aninverter;

FIG. 38 is a schematic block diagram showing another embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described in detailhereinbelow with reference to FIGS. 1 to 11. The invention isconstituted on the assumption that a variable speed motor is used as adrive source of a vacuum cleaner (fan motor). As a variable speed motor,it is considered to use an AC commutator motor whose speed is changed bycontrolling the input, a phase controlled motor, an induction motorwhich is driven by an inverter, a reactance motor, a brushless motorwhich is driven by an inverter, or the like. This embodiment will beexplained with respect to an example using a brushless DC motor havingno mechanical brush, so that the life of the motor is long and thecontrol response speed is high.

FIG. 1 is a schematic diagram of a vacuum cleaner according to theinvention. In the diagram, reference numeral 1 denotes a vacuum cleanermain body; 2 is a hose; 3 and 4 wheels; 5 a power supply cord; 6 and 7filters; 8 a fan; 9 a brushless DC motor; and 10 an inverter controlunit. When an electric blower consisting of the fan 8 and brushless DCmotor 9 is driven by the inverter control unit 10, the air inhaledthrough the hose 2 passes along a path consisting of the filter 6, fan8, and filter 7 as indicated by arrows and is discharged from the vacuumcleaner main body 1. Thus, the fine particles of abraded powder whichmight come from a brush of the motor are not discharged from the vacuumcleaner, and at the same time, the smell due to sparks at the brush isnot generated, when using a brushless motor. Therefore, there is theadvantage that the user can perform the cleaning operation under cleancircumstances.

FIG. 2 shows details of a speed control unit consisting of the brushlessDC motor 9 and inverter control unit 10 in accordance with theinvention.

An AC power source 14 is rectified by a rectifier 15 and smoothed by acapacitor 16, so that a DC voltage E_(d) is supplied to an inverter 20.The inverter 20 has a conducting period of angle 120° comprisingtransistors TR₁ to TR₆ and flywheel diodes D₁ to D₆ connected thereto.The transistors TR₁ to TR₃ constitute a positive arm of the inverter.The transistors TR₄ to TR₆ constitute a negative arm of the inverter.The current supplying period of time (i.e. conducting period or angle)of each arm corresponds to the electric angle of 120° and is pulse widthmodulated (PWM). A resister R₁ of a relatively low resistance iscommonly connected between the emitter of each of the transistors TR₄ toTR₆ constituting the negative arm of the inverter and the anode terminalof each of the flywheel diodes D₄ to D₆.

The brushless DC motor 9 comprises a rotor 9b using permanent magnets oftwo poles as fields and a stator 9a into which armature windings U, V,and W are inserted. Since winding currents flowing through the armaturewindings U, V, and W also flow through the low resistor R₁, a loadcurrent I_(D) of the motor 9 can be detected by the voltage drop of thelow resistor R₁. The speed control circuit of the brushless DC motor 9mainly comprises: a magnetic pole position detecting circuit 12 todetect the position of the magnetic pole of the rotor R using a Halldevice 11 or the like; a current detecting circuit 17 for detecting theload current I_(D) ; a base driver 19 to drive the transistors TR₁ toTR₆ ; and a microcomputer 13 to drive the base driver 19 on the basis ofdetection signals obtained from the detecting circuits 12 and 17.Numeral 18 denotes an operation switch which is operated by the actualuser.

The magnetic pole position detecting circuit 12 receives a signal fromthe Hall device 11 and produces a position detection signal 12S of therotor 9b. The position detection signal 12S is used to switch thecurrents of the armature windings U, V, and W and is also used as thesignal to detect the rotational speed. The microcomputer 13 obtains thespeed by counting the number of position detection signals 12S within apredetermined sampling time.

The current detecting circuit 17 detects the voltage drop of theresistor R₁ to obtain the load current I_(D), and a current detectionsignal 17S is obtained by an A/D converter (not shown).

The microcomputer 13 comprises: a central processing unit (CPU) 13a; aread only memory (ROM) 13b; and a random access memory (RAM) 13c.Although not shown, these components are mutually connected by anaddress bus, a data bus, a control bus, etc. The programs necessary todrive the motor 9, for example, the programs for the process tocalculate the speed, the process to fetch a speed command, the processto control the speed, etc. are stored in the ROM 13b. In addition, afunction table 22 in which various kinds of arbitrary speed controlpatterns are stored is provided in the ROM 13b.

The RAM 13c comprises: a memory section to read and write various kindsof data necessary to execute the foregoing various kinds of processingprograms; and a memory section in which speed pattern data relative tothe value of the winding current to be supplied at every position of therotor is stored.

The transistors TR₁ to TR₆ are respectively driven by the base driver 19in response to an ignition signal 13S which was processed and producedby the microcomputer 13. A voltage command circuit 21 produces a choppersignal, which will be explained hereinafter.

Since the winding currents flowing through the armature windings U, V,and W of the motor 9 correspond to the output torque of the motor 9, theoutput torque can be varied by changing the winding currents. Namely, byadjusting the load current I_(D), the output torque can be continuouslyarbitrarily changed. In addition, by changing the driving frequency ofthe inverter 20, the rotational speed can be freely changed.

The characteristic of the vacuum cleaner is as shown in FIG. 3. In FIG.3, the abscissa denotes the air flow amount Q (m³ /min) of the vacuumcleaner and the ordinate indicates the suction power P_(out)representative of the suction performance, the rotational speed N of themotor, and the load current I_(D). The region bounded by phantom linesindicates the actual operating range.

When the filter is choked only to a slight degree, the wind airflowamount Q is maximum and the rotational speed N is minimum. As the degreeof choking progresses, the operating point gradually moves to the leftand when the filter is completely choked, the air flow amount Q isminimum and the rotational speed N is maximum and the operating pointreaches the minimum point. The suction power P_(out) decreasesirrespective of the choking amount of the filter in the ranges beforeand after the maximum suction power P_(max) as a turning point.Therefore, by controlling the rotational speed of the motor to theoptimum speed in accordance with the choking amount of the filter, it ispossible to provide in the vacuum cleaner an improved suction powerP_(out).

A method of detecting the state or kind of cleaning surface will now bedescribed. In this embodiment, attention is paid to the fact that theminimum or maximum rotational speed, the average rotational speed, orthe fluctuating state of the rotational speed varies in dependence onthe cleaning surface. The cleaning surface is presumed from therotational speed, thereby controlling the motor to perform the optimumoperation according to the presumed, state of the cleaning surface.

FIGS. 4A and 4B show fluctuations in rotational speed of the motor inthe case of cleaning a tatami mat. (Japanese straw matting). Thesediagrams show the fluctuations in rotational speed which were actuallyconfirmed by experiments. FIG. 4A shows the case where the air flowamount Q is large in the state in which the filter is not choked. FIG.4B shows the case where the air flow amount Q is small in the state inwhich the filter is choked. As will be obvious from these diagrams, whenthe cleaning was performed by the cleaner whose air flow amount islarge, i.e. has a relatively clean filter the rotational speed of themotor varied from a minimum speed N₁₁ to the maximum speed N₁₂. On theother hand, when the cleaning was performed by the cleaner in which thefilter was somewhat chocked, the rotational speed of the motor variedfrom the minimum speed N₁₃ to the maximum speed N₁₄. As will be clearlyunderstood from the comparison between these two cases in the case ofthe cleaner in the choking state, the minimum speed N₁₃ is higher thanthe minimum speed N₁₁ when the filter is not choked. Likewise, themaximum speed N₁₄ is also higher than the maximum speed N₁₂. Therefore,for example, if the minimum speed N₁₁ is stored in the ROM 13b or RAM13c and compared with the minimum speed N₁₃ when the cleaner wasactually operated, the choking state of the filter can be detected. Areference value of the rotational speed which is stored in the ROM 13bor RAM 13c is not limited to only the value of N₁₁ but may be set toN₁₂, N₁₃, or N₁₄. If the degree of the choking state is high, thedifference between the rotational speeds is large. Therefore, byincreasing the input so as to raise the rotational speed in accordancewith this difference, a desired suction force of the cleaner can beobtained and the suction power P_(out) can be also improved.

As explained above, although the rotational speed of the motor of thecleaner varies in dependence on the choking state of the filter, it isactually largely influenced by the state of the cleaning surface. Sincethe cleaning surface is instantaneously changed during a single cleaningoperation in a manner such that it is changed from the floor to a carpetor from a tatami mat to a curtain, a fluctuation in rotational speedoccurs due to the change in cleaning surface, i.e., during a singlecleaning operation when considering the time cycle. However, by properlysetting the sampling time, the change in cleaning surface can be alsodetected.

This state is shown in FIG. 5. In FIG. 5, the abscissa denotes thesurface or object to be cleaned and the ordinate indicates therotational speed. Although there are various kinds of cleaning surfacesand objects to be cleaned, four kinds of typical cleaning surfaces andobjects, such as tatami mat, a carpet, a sofa, and a curtain arerepresented in this diagram. In the diagram, a solid line shows therotating state in the case where the filter is not choked and a brokenline indicates the rotating state in the case where the filter ischoked. Namely, the rotational speed is the-lowest in the case of tatamimat and sequentially increases in accordance with the order of carpet,sofa, and curtain. This tendency is derived irrespective of the chokingstate of the filter. However, as the choking state progresses, there isa tendency for the difference between the rotational speeds decreaseeven when the kind of cleaning surface changes. Although the rotationalspeeds N₁ to N₄ for the respective cleaning surfaces vary even when theyare cleaned, respectively, each of those speeds represents the minimumrotational speed or average rotational speed. When the vacuum cleaner isoperated for a long time in a closed room, the air is not circulated inthe room and the heat cannot be radiated, so that the temperatureincreases and there is a fear of burning of the motor. To avoid this, abypass passage is provided for the main air passage. In general, thebypass passage takes the outside air from portions other than thesuction port and feeds cooling air to the electric blower. The inside ofthe cleaner is cooled by this cooling air and thereafter, the coolingair is discharged to the outside. The indication of the operation of abypass valve in FIG. 5 indicates the position at which the valve is madeoperative to open the bypass passage when the suction port is completelyclosed. The bypass valve functions as a protecting apparatus to preventthe rotational speed from rising to a value which is equal to or higherthan the speed indicated by the position of the bypass valve operationin FIG. 5.

As explained above, when the cleaning surface and object to be cleanedchange and when the choking state fluctuates, the rotational speedvaries. Therefore, in addition to accurately detect the choking state,it is also necessary to detect the cleaning surface and object in orderto provide an optimum operation of the cleaner in accordance with thecleaning surface and object.

FIG. 6 shows the fluctuation modes of the rotational speed for everycleaning surface and every object in the case where the cleaningoperation is executed by use of the cleaner having a filter which is notchoked. Namely, similarly to FIG. 5, in FIG. 6, the abscissa indicatestime and represents different types of cleaning surface, while theordinate represents the rotational speed. In particular, each of thefluctuation modes M₁ to M₄ shown in the circles indicates a change inrotational speed during the cleaning operation for each cleaningsurface.

As is obvious from this diagram, when the cleaning surface is a tatamimat, the minimum speed is N₁₁ and the maximum speed is N₁₂ and afluctuation in rotational speed is small within a predetermined samplingtime. The minimum rotational speed at this time is N₁ shown in FIG. 5.

In the case of a carpet, the minimum speed is N₂₁ and the maximum speedis N₂₂ and the difference between the minimum and maximum speeds withinthe same sampling time as that mentioned above is larger than that inthe case of the tatami mat. The minimum speed at this time is N₂.

The waveforms of vibration in the fluctuation modes of the rotationalspeeds in the cases of the tatami mat and carpet are similar althoughthe fluctuation differences between the minimum and maximum speeds ofthe average rotational speeds are different.

In the case of a sofa, the minimum speed is N₃₁ and the maximum speed isN₃₂. The difference between them within the same sampling time is evenlarger than that in the case of the carpet. At this time, the minimumspeed is N₃. The waveform in the fluctuation mode in the case of thesofa is similar to a square wave.

In the case of a curtain, the minimum speed is N₄₁ and the maximum speedis N₄₂ and the difference between them within the same sampling time isstill larger than that in the case of the sofa. The minimum speed is N₄.The waveform in the fluctuation mode in the case of the curtain is alsosimilar to a square wave similar to the case of the sofa.

It can be considered that each of the minimum rotational speeds N₁₁,N₂₁, N₃₁, and N₄₁ corresponds to the open state in which the suctionport was removed from the cleaning surface. However, the averagerotational speed can be also used in place of the minimum rotationalspeed.

As is obvious from the above explanation, it will be understood that thecharacteristic of the surface or object which is actually being cleanedcan be detected from the average or minimum rotational speed and thefluctuation modes M₁ to M₄ of the motor of the cleaner and that thechoking state can be also detected.

On the other hand, when considering the cleaning surface or object to becleaned, it is the carpet from which it is most difficult to fetch dust.Therefore, when it is decided that the cleaning surface is a carpet oran object similar to a carpet, it is desirable to set the rotationalspeed into the highest speed. Next, it is preferable to sequentially setthe rotational speed in accordance with the tatami mat, sofa, andcurtain so as to gradually decrease. Namely, it was desirable to assumethe rotational speeds as mentioned above in consideration of theeasiness in fetching of dust and a phenomenon and state in which thesuction port is attracted to the cleaning surface or the like.

Namely, since the cleaning surface or object or the choking state can bedetected from FIG. 6 and the like, by setting the optimum rotationalspeed in accordance with the choking state detected, the cleaningoperation can be performed in accordance with the cleaning surface.

Practical control means will now be explained.

FIG. 7 shows control patterns stored in the ROM 13b in the microcomputer13. Practically speaking, these patterns are stored as function tables22 corresponding to the respective cleaning surfaces. In this diagram,the abscissa denotes a degree of the choking state and the ordinateindicates a speed command N*. The rotational speed is set from theforegoing necessary rotational speeds in accordance with the order ofcarpet, tatami mat, sofa, and curtain and is set so as to increase asthe choking state progresses. Due to this, the function in the functiontable 22 is automatically set in accordance with the cleaning surface.The cleaning surface such as a carpet or the like is not limited to thecarpet. It is also possible to consider in a manner such that thefunction for a carpet is used in the case of the cleaning surface havinga characteristic similar to that of the carpet. The same shall alsoapply to the cases of tatami mat, sofa, and curtain. Further, bycalculating the speed command N* in accordance with the degree ofchoking state, the speed command N* corresponding to not only thepresumed cleaning surface but also the degree of choking state isderived and the optimum control can be accomplished.

FIG. 8 shows the content of the processes which are executed by themicrocomputer 13. This diagram shows a procedure to obtain the speedcommand N* in accordance with the characteristic of the cleaning surfaceand the degree of choking of the filter.

In the process I, the rotational speed of the motor 9 which changes withan elapse of time is calculated using the position detection signal 12S.

In the process II, the maximum speed N_(max) and the minimum speedN_(min) within a sampling time T are detected.

In the process III, the mode of the rotational vibration, namely, thevibration frequency and the value of amplitude within the sampling timeare compared with the vibration mode (fluctuation mode of the speed)which has previously been stored in the ROM 13b, thereby detecting thecharacteristic of the cleaning surface and the degree of choking of thefilter from the rotational speeds N_(max) and N_(min).

In the process IV, a predetermined value corresponding to the chokingstate is selected from the function table 22 selected on the basis ofthe cleaning surface and the degree of choking, thereby obtaining thespeed command N* in accordance with this value.

A control circuit to realize this processing method will now beexplained with reference to FIG. 9. Various kinds of speed controlsystems such as ASR, ACR, and the like are considered. In FIG. 9, avoltage controlled system having a closed loop is shown. In the diagram,when the user of the cleaner turns on the operation switch 18, anoperation command is fetched to start the brushless DC motor 9. When therotational speed rises to a predetermined speed, the activating processis finished. Thereafter, the processes to determine the cleaning surfaceand to detect the degree of choking state are executed.

The microcomputer 13 shown in FIGS. 2 and 9 receives the positiondetection signal 12S from the magnetic pole position detecting circuit12 and calculates the rotational speed in the process I in FIG. 8. Inthe next process II, the maximum speed N_(max) and the minimum speedN_(min) are detected. Further, the microcomputer 13 determines thecharacteristic of the cleaning surface and the choking state of thefilter in the process III on the basis of the detected maximum andminimum speeds. Subsequently, in the process IV, a predeterminedfunction table 22 is selected by a switch 23 in accordance with thecleaning surface and choking state. The speed command N* is obtained onthe basis of a predetermined speed command value in the function table22 selected in accordance with the degree of choking of the filter. Thespeed command N* is converted into a voltage command V* by a gain K. Thevoltage command V* is input to a D/A converter. An output of the D/Aconverter is compared with an output of a triangular wave generator,which is provided separately from the D/A converter, by a comparatorprovided at the output stage. An output corresponding to the differencebetween those outputs is supplied to the base driver 19. The base driver19 applies the voltage based on the voltage command which was determinedto the motor 9.

In this manner, the motor 9 is rotated at the required speed in responseto the speed command N* according to the cleaning surface and the degreeof choking of the filter

FIG. 10 shows performance curves of a cleaner (electric blower) usingthe motor 9 which is controlled as explained above to drive the vacuumcleaner. FIG. 10 is similar to that described in FIG. 3. In FIG. 10,broken lines indicate the case where the filter is not choked and solidlines represent the case where the filter is choked. As is obvious fromthis diagram, as the choking state of the filter progresses, bydetecting this choking state and by increasing the rotational speed inaccordance with the degree of choking, the suction power P_(out) whichwas reduced due to the choking can be raised as shown by the solidlines, so that a vacuum cleaner having a high efficiency can beobtained.

FIG. 11 similarly shows a change in performance to the cleaning surface.This diagram shows changes in suction power P_(out), rotational speed N,and load current I_(D) which are necessary in accordance with the typeof cleaning surface. The optimum rotational speed N* is given inaccordance with the characteristic responsive to the choking state ofthe filter on the basis of the function table 22 corresponding to thecleaning surface.

Although the control of the cleaner has been accomplished using only thebrushless DC motor 9, it can be also attained by use of a variable speedmotor.

FIG. 12 shows another embodiment of the invention. In the diagram, aphase controlled AC commutator motor 24 comprises a field winding 24Aand an armature 24B. The motor 24 is connected to the AC power source 14through a phase control unit 25 including a control device such astriac, FLS, thyristor, or the like. An ignition angle of a gate of thecontrol device of the phase control unit 25 is controlled by a driver 27similar to the base driver 19 shown in FIG. 2. The microcomputer 13 alsohas the processing function similar to that mentioned above. Namely, themicrocomputer 13 determines the characteristic of the cleaning surfaceon the basis of the maximum speed N_(max) and the minimum speed N_(min)within the sampling time on the basis of the rotation information(mainly, rotational speed information) derived from a rotation detector26, thereby producing a gate signal of the control device by furtherconsidering the choking state of the filter. The content of thepractical processes which are executed by the microcomputer is similarto that shown in FIG. 8. In this embodiment, it is also possible toprovide a cleaner having the optimum suction state according to thepresumed cleaning surface and choking state and the cleaning efficiencydoes not deteriorate.

According to the foregoing embodiment, it is possible to obtain acleaner having an optimum suction performance in accordance with thecleaning surface and the choking state of the filter. However, since thecleaning surface is presumed from the rotational speed, when it has beenpresumed that the cleaning surface is a tatami mat, this surface is notalways a tatami mat. In other words, this presumed cleaning surface is asurface having the same surface characteristic as that of a tatami mator the cleaning surface in the state similar to the tatami mat.

In any case, the rotational speed is controlled in accordance with thestate of the cleaning surface or controlled so as to compensate thesuction performance which was determined due to the choking of thefilter. Thus, an optimum control of the cleaner can be automaticallyattained.

As is obvious from the above description, the rotational speed can bedetected by directly using the signal of the Hall device 11 in themagnetic pole position detecting circuit 12 which is generally used in,for example, the brushless DC motor 9, so that what is called asensorless vacuum cleaner is derived.

An explanation will now be made with respect to a practical example of avacuum cleaner in which the speed control of the brushless DC motor canbe performed to achieve an optimum condition in accordance with a changein load of the vacuum cleaner.

FIGS. 13 to 15 show another embodiment of the invention. A speed controlunit in this case is as shown in FIG. 13 and differs from the speedcontrol unit shown in FIG. 2 with respect to two points that a speedcommand circuit 180 is used in place of the operation switch 18 and thatthe voltage command circuit 21 is omitted. In FIG. 13, the parts andcomponents having the same functions as those shown in FIG. 2 aredesignated by the same reference numerals.

FIG. 15 shows performance curves of a vacuum cleaner, in which theabscissa denotes an amount Q of air flow which was inhaled from the hose2 and the ordinate represents a suction power P_(out) indicative of thesuction performance of the cleaner and a rotational speed N and a loadcurrent I_(D) of the motor. Solid lines indicate the case where aconventional AC commutator motor was used and broken lines represent thecase where the brushless DC motor was used. A range from the maximumoperating point to the minimum operating point is the operating range ofthe vacuum cleaner.

Namely, in the case of using the conventional AC commutator motor, thesuction power P_(out) increases from the maximum operating point (in thestate in which the suction port of the hose was removed from an objectto be cleaned, or the like) with a decrease in air flow amount andreaches the maximum value. When the air flow amount further decreases,the suction power P_(out) is reduced and reaches the minimum operatingpoint (in the state in which the filter is choked, the suction port isclosed, or the like). In general, in the case where a tatami mat orcarpet is cleaned, the operating point is located on the side where theair flow amount is small from the maximum point of the suction P_(out)and the cleaner is actually used in the range where the suction powerP_(out) is small. Therefore, when the cleaner has inhaled dust and thedust is accumulated, the suction capability of the vacuum cleanerlargely deteriorates. This is because, since the load current I_(D) ofthe AC commutator motor decreases with a reduction in air flow amountand an increase in the degree of the rotational speed in the range fromthe maximum operating point to the minimum operating point is small, theoutput of the motor is reduced.

Therefore, it is sufficient for the vacuum cleaner to rotate the fan ata high speed in response to the decrease in air flow amount. When thefan is rotated at a high speed, a torque T also increases. In otherwords, the current also rises. Therefore, as shown in FIG. 15, althoughthe brushless DC motor generally exhibits a shunt characteristic, byperforming a series wound control so as to increase the rotational speedwith a decrease in air flow amount, the motor can obtain acharacteristic as shown by broken lines. Thus, there is an effect suchthat the suction power P_(out) at an operating point near the minimumoperating point can be improved.

FIG. 14 shows the order of the processing operations which are executedby the microcomputer.

Namely, when a start command is input, the motor is rotated to apredetermined rotational speed. Thereafter, by performing the serieswound control by detecting the load state, the characteristic as shownin FIG. 15 is derived.

Practically speaking, the state in which the motor is held in thestandby mode until a start command is input is repeated. When the speedcommand serving as a reference speed is input from the speed commandcircuit 180 to the microcomputer 13, the microcomputer 13 detects theposition of the magnetic pole and outputs a position detection signaland controls the speed (controls the voltage or current which is appliedto the motor) on the basis of the calculated speed. The activation modeis repeated until the rotational speed reaches the speed command value.When the rotational speed has reached the speed command value, themicrocomputer 13 enters the series wound control mode and detects theposition of the magnetic pole and outputs the position detection signal.Then, the microcomputer calculates the load state of the cleaner on thebasis of the result of the speed obtained and the detection value of theload current and controls the speed on the basis of the load stateobtained so as to exhibit a predetermined series wound characteristic.The series wound control mode is repeated. The actual speed is comparedwith the speed command value in each mode. When no speed command exists(i.e., when a stop command is input), the motor is stopped and the motoris set into the standby mode to wait for the input of a start command.These operations are repeated. Thus, it is possible to provide a vacuumcleaner which can increase the power (improve the suction powerindicative of the suction performance) of the cleaner.

FIGS. 16 to 18 show another embodiment of the invention. In this case, aspeed control unit is as shown in FIG. 17 and differs from the speedcontrol unit shown in FIG. 13 with respect to a point that the voltagecommand circuit 21 is provided. In FIG. 17, the parts and componentshaving the same functions as those shown in FIG. 13 are designated bythe same reference numerals.

In FIG. 16, when a command is input from the speed command circuit 180to the microcomputer 13, the microcomputer 13 reads the command andoutputs a speed command N*. The speed command N* is input to a D/Aconverter of the voltage command circuit 21. An output of the D/Aconverter is compared with an output of the triangular wave generator bythe comparator. An output of the comparator is input to the base driver17, so that the voltage which is applied to the motor 9 is determined.In response to the position detection signal 12S from the magnetic poleposition detecting circuit 12, the microcomputer 13 calculates therotational speed N. The speed N is compared with the command value N".Thus, the motor 9 is controlled so as to always rotate at the speedinstructed by the speed command N*.

Further, the current detection signal 17S of the current detectingcircuit 17 is input to the microcomputer 13. The microcomputer 13calculates the load current I_(D) and obtains the difference I_(D1)-I_(D)) between a reference value I_(D1) and the load current I_(D). Themicrocomputer 13 also calculates ΔN by a gain K₀ and is added to thespeed command N*. Thus, the speed command N* is corrected by the valueof the load current I_(D) corresponding to the load change and the motor9 is operated by the closed loop speed control on the basis of the newspeed command N*+ΔN. Therefore, the rotational speed increases with adecrease in load current I_(D), so that the series wound characteristicis derived. There is an effect such that a vacuum cleaner having animproved suction performance is obtained.

FIG. 18 shows performance curves of a vacuum cleaner in which abrushless DC motor is driven by a speed control unit according to theinvention. In the diagram the abscissa denotes an amount Q of air whichflows in the vacuum cleaner and the ordinate represents suction powerP_(out) indicative of the suction performance of the vacuum cleaner, arotational speed N and a load current I_(D) of the motor. The range fromthe maximum operating point to the minimum operating point is theoperating range of the vacuum cleaner. Broken lines indicate the casewhere the motor is continuously operated by the ordinary closed loopspeed control. Since the rotational speed N is constant to a change inair flow amount Q, the suction power P_(out) is small and a desiredperformance as a vacuum cleaner is not obtained. On the other hand,solid lines show the case where the motor is operated by the closed loopspeed control of this embodiment. Since the speed correction amount ΔNis obtained from the difference (I_(D1) -I_(D)) corresponding to thedecreased amount of the load current I_(D) from the reference loadcurrent I_(D1) due to the change in air flow amount Q, the rotationalspeed increases in a square manner (i.e. in an accelerated manner) witha decrease in air flow amount Q. Thus, there is an effect such that avacuum cleaner in which the suction power P_(out) is large and thesuction performance is improved is derived.

FIGS. 19 and 20 show another embodiment of the invention. In this case,a speed control unit uses the speed control unit shown in FIG. 17. InFIG. 19, when a command is input from the speed command circuit 180 tothe microcomputer 13, the microcomputer 13 reads the command anddetermines the speed command N* and outputs the voltage command V* by again K₁. The voltage command V* is input to the D/A converter of thevoltage command circuit 21. An output of the D/A converter and an outputof the triangular wave generator are compared by the comparator. Anoutput of the comparator is input to the base driver 19, so that thevoltage which is applied to the brushless DC motor 9 is decided. Thus,the motor 9 is operated by the closed loop voltage control based on thespeed command N*. Therefore, the rotational speed changes by thedrooping characteristic of the motor in dependence on the load change ofthe cleaner (for example, the change of the surface to be cleaned whenthe filter of the cleaner main body is choked and the suction port is incontact with the floor surface, or the like). When the load is light,the rotational speed increases. When the load is heavy, the speeddecreases. Namely, the same characteristic as that of the AC commutatormotor which is used in a current vacuum cleaner is obtained. There is aneffect such that the motor control suitable for the vacuum cleaner canbe performed.

Further, an output of the current detecting circuit 17 is input to themicrocomputer 13. The microcomputer 13 calculates the load current I_(D)and obtains the difference (I_(D1) -I_(D)) between the reference valueI_(D1) and the load current I_(D). ΔV is calculated by a gain K₂ andadded to the voltage command V*. Thus, the voltage command V* iscorrected (in other words, the speed command N* is corrected) by thevalue of the load current I_(D) corresponding to the load change and thebrushless DC motor 9 is operated by the open loop voltage control on thebasis of the new voltage command V*+ΔV. Thus, there are effects suchthat the variable range of the rotational speed is widened, the serieswound characteristic is accomplished, and a vacuum cleaner in which thesuction performance is improved is obtained.

FIG. 20 shows performance curves of a vacuum cleaner in which abrushless DC motor was driven by the speed control unit of theinvention. In the diagram, the abscissa denotes an amount Q of air flowwhich flows in the vacuum cleaner and the ordinate represents suctionpower P_(out) representative of the suction performance of the vacuumcleaner, a rotational speed N and a load current I_(D) of the motor. Therange from the maximum operating point to the minimum operating point isthe operating range of the vacuum cleaner. Broken lines indicate thecase where the motor was operated by the ordinary closed loop speedcontrol. Since the rotational speed N is constant to a change in airflow amount Q, the suction power P_(out) is small and a desiredperformance of the vacuum cleaner is not derived. On the other hand,solid lines show the case where the motor was operated by the open loopvoltage control of the invention. Since the rotational speed increaseswith a decrease in air flow amount Q, the suction power P_(out) is largeand a desired performance of the vacuum cleaner is derived. Further,alternate long and short dash lines represent the case where the motoris operated by the series wound feature of the invention. The voltagecorrection amount ΔV is derived from the difference (I_(D1) - I_(D))corresponding to the decreased amount of the load current I_(D) from thereference load current I_(D1) due to the change in air flow amount Q, sothat the rotational speed increases in a square manner with a decreasein air flow amount Q. Thus, there are effects such that the suctionpower P_(out) further rises and the vacuum cleaner in which the suctionperformance is improved is obtained.

FIGS. 21 to 23 show another embodiment of the invention. In this case, aspeed control unit is as shown in FIG. 22 and differs from the speedcontrol unit shown in FIG. 17 with respect to a point that a currentcommand circuit 210 is used in place of the voltage command circuit 21.In FIG. 22, the parts and components having the same functions as thoseshown in FIG. 17 are designated by the same reference numerals.

In FIG. 21, when a command is input from the speed command circuit 180to the microcomputer 13, the microcomputer 13 reads this command andproduces the speed command N* and outputs a current command I_(D) * by again K₁₁. The current command I_(D) * is input to a D/A converter 210ain the current command circuit 210. An output of the D/A converter 210aand an output of a triangular wave generator 210b are compared by acomparator 210c. An output of the comparator 210c is input to the basedriver 19 and the voltage which is applied to the brushless DC motor 9is determined. An output of the current detecting circuit 17 is input tothe microcomputer 13. The microcomputer 13 calculates the load currentI_(D) and compares it with the current command I_(D) *. Thus, the motor9 is controlled so as to always rotate at the speed instructed by thecurrent command I_(D) *.

Further, in response to a detection signal from the magnetic poleposition detecting circuit 12, the microcomputer 13 calculates the speedand obtains the difference (N-N₁) between the rotational speed N and thereference value N₁ and obtains ΔI_(D) by a gain K₂₁ and compares it withthe current command I_(D) *. Thus, the current command I_(D) * iscorrected (in other words, the speed command is corrected) by the valueof the rotational speed N corresponding to the load change and the motor9 is operated by the closed loop current control (this control isreferred to as the series wound control) on the basis of the new currentcommand I_(D) *-I_(D), so that the variable range of the rotationalspeed is widened.

FIG. 23 shows performance curves of a vacuum cleaner in which thebrushless DC motor was driven by the speed control unit of theinvention. In the diagram, the abscissa denotes an amount Q of air whichflows in the vacuum cleaner and the ordinate indicates suction powerP_(out) representative of the suction performance of the vacuum cleaner,a rotational speed N and a load current I_(D) of the motor. The rangefrom the maximum operating point to the minimum operating point is theoperating range of the vacuum cleaner. Broken lines indicate the casewhere the motor is operated by the ordinary closed loop speed control.Since the rotational speed N is constant to a change in air flow amountQ, the suction power P_(out) is small and a desired performance of thevacuum cleaner is not obtained. On the other hand, solid lines show thecase where the motor is operated by the closed loop current control ofthe invention. When the air flow amount Q decreases, the load torque isalso reduced. Therefore, when the closed loop current control isperformed, the rotational speed N increases in a square manner with adecrease in air flow amount Q, so that the suction power P_(out) islarge and a desired performance of the vacuum cleaner is obtained.Further, alternate long and short dash lines indicate the case where themotor is operated by the series wound control of the invention. Thecurrent correction amount ΔI_(D) is obtained from the difference (N-N₁)corresponding to the increased amount of the rotational speed N from thereference rotational speed N₁ due to the change in air flow amount Q andcompared with the current command I_(D) *. Thus, an increase inrotational speed N due to a change in air flow amount Q can besuppressed and the series wound characteristic can be obtained. Byarbitrarily setting the current correction amount ΔI_(D), the changerange of the rotational speed N can be widened. Thus, there are effectssuch that the change range of the rotational speed is widened and thesuction power P_(out) can be arbitrarily adjusted and a vacuum cleanerin which the suction performance is improved is obtained.

FIGS. 24 to 27 show another embodiment of the invention. In this case, aspeed control unit uses the speed control unit shown in FIG. 17.

FIG. 24 shows performance curves of a vacuum cleaner in which abrushless DC motor is used as a drive source. In the diagram, theabscissa denotes an amount Q of air which flows in the vacuum cleanerand the ordinate indicates suction power P_(out) representative of thesuction performance of the vacuum cleaner, a rotational speed N and aload current I_(D) of the motor. The range from the maximum operatingpoint to the minimum operating point is the operating range of thevacuum cleaner. The position near the maximum operating pointcorresponds to the state in which the suction port is away from thesurface to be cleaned and at this time, the maximum electric power isneeded. On the other hand, the position near the minimum operating pointcorresponds to the state in which the suction port is closely in contactwith the floor surface and at this time, the electric power is minimum.

The load state of the vacuum cleaner is light in the case of the floorsurface such as, e.g., tatami mat, carpet, etc. and the position nearthe maximum suction power corresponds to the operating point. Namely,the substantial operating range falls within a range from the point ofthe maximum suction power to the minimum operating point. On the otherhand, as mentioned before the position near the minimum operating pointcorresponds to the state in which the suction port is closely in contactwith the floor surface. Therefore, the cleaning work of the cleaner isnot performed. On the contrary, the suction port is hardly removed fromthe floor surface and it is hard for the user to handle the cleaner toperform the cleaning.

To avoid such a problem, in order to effectively use the electric power,according to the invention, when the user is performing the cleaning byvacuuming dust using the cleaner, the brushless DC motor is rotated atthe full power and the electric power is saved in other cases.

FIG. 25 shows performance curves of a vacuum cleaner having the powersaving function. In the diagram, the abscissa and the ordinate indicatethe same contents as those shown in FIG. 24. Broken lines show the casewhere the power saving was performed by the low output open loopcontrol. Solid lines represent the case where the speed control wasperformed by high output open loop control. Namely, the rotational speedof the brushless DC motor is increased to the speed at the maximumoperating point A₂ by an inverter control unit and the speed control isperformed by the low output open loop. At this time, the motor is in thepower saving state and the rotational speed is low, so that the level ofthe sound which is generated from the cleaner can be reduced and at thesame time, the electric power consumption can be saved. Next, since thespeed control is executed by the open loop, when the load conditionchanges (so as to reduce the load), the load current of the brushless DCmotor decreases. When the load current I_(D) is reduced to I₂, thecontrol mode is switched from the low output open loop control to thehigh output open loop control and the motor is fully rotated along thesolid line on which the rotational speed changes in dependence on theair flow amount. On the other hand, when the rotational speed of thebrushless DC motor rises and reaches N₁, the operating mode is alsoswitched to the power saving state (low output open loop control). Inthis state, when the load condition changes so as to contrarily increasethe load, the load current I_(D) of the motor increases. When the loadcurrent I_(D) reaches I₁, the control mode is again switched to the highoutput open loop control, and the motor is fully rotated in a mannersimilar to the foregoing case. When the rotational speed of the motordecreases and reaches N₂, the operating mode is switched to the powersaving state (low output open loop control) and the motor is returned tothe original state.

Thus, the load state can be discriminated without using a load statesensor (air flow amount sensor or the like). Only when the user performsthe cleaning work, the brushless DC motor is fully rotated and theelectric power can be saved in the other cases. There are effects suchthat the sound level can be reduced and the electric power consumptioncan be saved in the standby mode of the cleaner.

FIG. 26 is a schematic block diagram of a control circuit to accomplishthe performance of FIG. 25. In the diagram, when a command is input fromthe speed command circuit 18 to the microcomputer 13, the microcomputer13 reads the command and first selects a gain K₁₂ (gain when the lowoutput open loop control is performed) and supplies the voltage outputdata to the D/A converter in the voltage command circuit 21. An outputof the D/A converter is compared with an output of the triangular wavegenerator by the comparator. An output of the comparator is input to thebase driver 19. The voltage (or current) which is applied to thebrushless DC motor 9 is determined. The motor enters the power savingstate.

In response to a detection signal from the magnetic pole positiondetecting circuit 12, the microcomputer 13 calculates the speed. Inresponse to a detection signal from the current detecting circuit 17,the microcomputer 13 calculates the current. On the basis of the speedand current calculated, the switching state is decided. When the cleaneris set into the cleaning mode, the gain K₁₂ is switched to a gain K₂₂(gain when the high output open loop control is performed: K₁ <K₂) andthe brushless DC motor is fully rotated.

FIG. 27 shows the order of the processing operations of themicrocomputer in this embodiment.

Namely, the activation waiting state is repeated. When an activationcommand is input, the brushless DC motor is rotated to a predeterminedrotational speed (rotational speed at the maximum operating point).Then, the low output open loop control is executed and the cleaner isset into the power saving state. If the load current I_(D) is smallerthan I₁ or larger than I₂, the low output open loop control iscontinued. Next, when the load current I_(D) falls within a range fromI₁ to I₂ (I₁ <I_(D) <I₂), the high output open loop control is performedand the motor is fully rotated. When the rotational speed N lies withina range from N₁ to N₂ (N₁ <N<N₂), the high output open loop control iscontinued. When the rotational speed N is higher than N₁ or lower thanN₂, the low output open loop control is executed and the cleaner is setinto the power saving state.

Therefore, according to another embodiment when the user is performingthe cleaning work using the cleaner, the motor is fully rotated and thecleaner is operated in the power saving mode in the cleaning standbymode in the other cases. Thus, there are effects such that the soundlevel can be reduced and the electric power consumption can be saved.

FIGS. 28 to 30 show another embodiment of the invention. In this case, aspeed control unit uses the speed control unit shown in FIG. 17.

FIG. 28 shows performance curves of a vacuum cleaner in which abrushless DC motor is used in a drive source. In the diagram, theabscissa denotes an amount Q of air which flows in the vacuum cleanerand the ordinate indicates suction power P_(out) representative of thesuction performance of the vacuum cleaner, a rotational speed N and aload current I_(D) of the motor. The range from the maximum operatingpoint to the minimum operating point is the operating range of thevacuum cleaner. On the other hand, since the air flow amount Q decreasesin dependence on the degree of choking state, the operating point forthe chokes of the filter moves from the maximum operating point to theminimum operating point. Thus, as the degree of choking state increases,the suction power P_(out) decreases in the ranges before and after themaximum suction power P_(max) as a turning point and the performance ofthe vacuum cleaner is lacking. Further, when the degree of sealing inthe intake air passage rises because this passage is choked or foreignmatter is deposited therein, or the like, the rotational speed increasesmore than it is needed. Such a situation causes a problem in terms ofthe mechanical strength of the motor and the life of the bearing. Toavoid such a problem, according to the invention, the load current ofthe motor is detected and the operating mode is decided on the basis ofthe level of the load current. In particular, when the load current hasdecreased to a value which is equal to or lower than a predeterminedvalue, the rotational speed is set to a constant value, therebypreventing the over rotation.

FIGS. 29A and 29B show changes in load current to the operating mode.The point A₁ at which the air flow amount Q is large as shown in FIG. 3corresponds to the case where the filter is not choked. The differencebetween the load current I_(D) and the minimum current set value I_(DS)shown by a broken line is large. On the other hand, a point B₁ at whichthe air flow amount Q is small corresponds to the state in which thedegree of sealing rises because the filter is choked or foreign matteris inhaled in the intake air passage. The minimum value I_(D2) of thecurrent change is smaller than the minimum current set value I_(DS)shown by a broken line. Thus, the choking of the intake passage orfilter can be accurately decided by this value without using the sensor.

FIG. 30 is a schematic constitutional block diagram of a control circuitto drive a brushless DC motor of the invention. An open loop voltagecontrol system has been shown as an example of a speed control system.In the diagram, when a command is input from the speed command circuit180 to the microcomputer 13, the microcomputer 13 reads the command andoutputs the speed command N*. The microcomputer 13 first selects a gainK₁₃ and supplies the voltage output data V* to the D/A converter in thevoltage command circuit 21. An output f the D/A converter is comparedwith an output of the triangular wave generator by the comparator. Anoutput of the comparator is input to the base driver 19. The voltagewhich is applied to the brushless DC motor 9 is determined. The motor isrotated at the rotational speed corresponding to the reference voltage.

In response to the detection signal 12S from the load current detectingcircuit 12, the microcomputer 13 then compares the currents. A switchingdecision processing section determines whether the load current I_(D) issmaller or larger than the minimum current set value I_(DS). If the loadcurrent I_(D) is smaller than the minimum current set value I_(DS), itis determined that the filter is choked because of foreign matter(handkerchief, nylon sheet, etc.) is obstructing the intake air passage.Thus, the voltage correction amount ΔV is subtracted from the voltage bythe gain K₂₃, thereby correcting the voltage command (in other words,correcting the speed command) of the brushless DC motor. Therefore,there are effects such that the rotational speed of the motor is notincreased to a value greater than is needed and the overrotation can beprevented.

FIGS. 31 to 37 show another embodiment of the invention. FIG. 38 showsanother embodiment of the invention. Both of these embodiments relate toan apparatus to operate a motor such that a vacuum cleaner can use an ACpower source of any of the low and high voltage systems.

FIG. 31 shows a block diagram of a speed control unit of a brushless DCmotor. An AC voltage 116 of a AC power source 101 is converted into a DCvoltage E_(d) through a rectifier 102 and a step-up chopper circuit 103to improve the power factor. The DC electric power is supplied to aninverter 104. A winding 105a of a brushless DC motor 105 is driven bythe inverter 104.

A control circuit to control the speed of the motor 105 comprises amicrocomputer 106; a position detecting circuit 108 to detect theposition of the magnetic pole of a rotor 105b of the brushless DC motor105 from a motor terminal voltage 107; an inverter control section 109for transistors Q₁ to Q₆ constituting the inverter 104; a DC voltagecontrol section 111 to control the step-up chopper circuit 103 whilereferring to the waveform and level of a power source current 110; a DCvoltage comparing section 125 to decide whether the voltage system ofthe AC power source 101 is the low voltage system or the high voltagesystem; and a direct current detecting section 126 to detect a DCcurrent I_(d) flowing through the inverter 104.

Various kinds of programs necessary to drive the DC motor 105 are storedin the microcomputer 106. For example, the microcomputer 106 executesthe following processes: the process to control the speed; the processto fetch a position detection signal 112 from the position detectingcircuit 108, a speed command signal 113, a DC voltage comparison signal130, and a detected direct current 123; and the process to output aninverter drive signal 114, a current command signal 115 to the DCvoltage control section 111, and a voltage signal 124 to the invertercontrol section 109.

The chopper circuit 103 comprises a coil 103a, a transistor Q₇, a diode103b, and a smoothing capacitor 103c. A drive signal to the transistorQ₇ is produced by the DC voltage control section 111. By changing the ontime and off time of the transistor Q₇, the level of the power sourcecurrent 110 is changed.

FIG. 32 shows the relation between the power source voltage 116 and thepower source current 110. The waveform of the power source current 110is set to a sine wave of the same phase as that of the power sourcevoltage 116 by the chopper circuit 103 which is controlled by the DCvoltage control section 111 and at the same time, the effective value asthe magnitude of the sine wave is controlled in accordance with thecurrent command signal 115 which is output from the microcomputer 106,thereby setting the power factor of the power source to about 1.0.

The power source current control section 111 comprises a power sourcevoltage detecting circuit 111a to make a voltage signal 117 having thefull-wave rectified waveform synchronized with the power source voltage116 from an output voltage of the rectifier 102 a D/A converter 111bwith a multiplication to produce a sync current command signal 118 as ananalog signal by multiplying the voltage signal 117 with the currentcommand signal 115 as a digital signal; a power source current amplifier111c to convert the full-wave rectified waveform of the power sourcecurrent 110 into the voltage by a resistor R₁₀ and to detect andamplify; a current control amplifier 111d to compare a detection powersource current signal 119 as an output of the power source currentamplifier 111c with the sync current command signal 118, thereby settingthe difference voltage to 0; a comparator 111f to compare a differencesignal 120 as an output of the current control amplifier 111d with atriangular wave signal 121 as an output of a triangular wave oscillator111e, thereby making a chopper signal 122 for the transistor Q₇ ; and adriver 111g for the chopper for the transistor Q₇.

The inverter control section 109 comprises a D/A converter 109d toconvert the voltage control signal 124 as a digital signal which isoutput from the microcomputer 106 into an analog signal; a comparator109b to compare a voltage signal 127 as an output of the D/A converter109d with a triangular wave signal 128 as an output of a triangular waveoscillator 109c, thereby making a chopper signal 129 for the inverter104; and a driver 109a for the inverter 104.

The direct current detecting section 126 comprises: a direct currentamplifier 126a to convert a direct current I_(d) into a voltage by aresistor R₂₀ and to detect and the voltage amplify; and an A/D converter126b to convert an output of the direct current amplifier 126a into adigital signal.

The DC voltage comparing section 125 comprises a set voltage amplifier125a to amplify a DC set voltage E_(dc) ; and a comparator 125b tocompare an output of the set voltage amplifier 125a with the DC voltageE_(d) detected by resistors R₃₀ and R₄₀.

With the foregoing constitution, the reasons why the different controlmethods are used for the case where the AC power source 101 is of thelow voltage system and for the case where it is of the high voltagesystem and its switching method will now be explained hereinbelow.

A brushless DC motor 105 is speed controlled by changing an outputvoltage of the inverter 104. As a method of changing the output voltage,there are a method whereby the DC voltage E_(d) is changed by thestep-up chopper circuit 103 to improve the power factor and a methodwhereby the voltage which is applied to the motor 105 is changed by thePWM control by the inverter 104. According to the former method, sincethe chopper circuit 103 is used, when the DC voltage E_(d) is set to belower than the peak value of the power source voltage 116 of the ACpower source 101, the chopper circuit 103 is turned off and does notoperate at the position near the peak value of the power source voltage116, so that the power source current 110 cannot be controlled to a sinewave. To control the speed in such a range, it is necessary to performthe PWM control by the inverter 104 on the basis of the latter method.

On the other hand, when the same control method is used for the lowvoltage system and high voltage system, the voltage which is applied tothe motor 105 changes by twice/half of the applied voltage. To obtainthe same characteristic, two kinds of motors 105 which are energized bydifferent voltages are necessary. Therefore, different control methodsare used for the low voltage system and high voltage system by a methodwhich will be explained hereinbelow.

FIG. 33 shows the capacitor charging voltage E_(d) before the motor 105is activated. The capacitor voltage E_(d) is held at E_(d1) in the caseof the low voltage system and at E_(d2) in the case of the high voltagesystem. When a set voltage E_(dc) in the DC voltage comparing section125 is set to a value which is higher than E_(d1) and lower than E_(d2),the output signal 130 of the comparator 125b changes to the high levelfor the low voltage system and to the low level for the high voltagesystem.

FIG. 34 shows the content of processes which are executed by themicrocomputer 106. By fetching the output signal 130 of the DC voltagecomparing section 125, it is decided whether the initial chargingvoltage E_(d) of the capacitor 103c is of the low voltage system or ofthe high voltage system. When it is of the low voltage system, theinverter 104 is controlled by fixing the current supply angle to 120°and the DC voltage E_(d) which is output from the chopper circuit 103 ismade variable, thereby controlling the speed of the motor 105. In thecase of the high voltage system, the DC voltage E_(d) which is outputfrom the chopper circuit 103 is set to a fixed value and the inverter104 is controlled by setting the current supply angle to 120° and byperforming the PWM, thereby controlling the speed of the motor 105.

A practical example will not be explained. In the case of the lowvoltage system, as shown in FIG. 35, the DC voltage E_(d) is changedfrom E₀ to E_(dm) (the maximum value) by the chopper circuit 103 inaccordance with speed command signals N₁ * to N₂ *. FIGS. 36A and 36Bshow line voltages of one phase of the motor 105. Since the inverter 104is controlled by fixing the current supply to 120°, the applied voltageof the motor 105 varies depending on the chopper circuit 103. The speedof the motor 105 is controlled by the chopper circuit 103.

in the case of the high voltage system, as shown in FIGS. 37A and 37B,the chopper circuit 103 is controlled such that the DC voltage E_(d) isset to a constant value of E_(dm) (the maximum voltage for the lowvoltage system) and the inverter 104 is controlled by fixing the currentsupply angle to 120° and by performing the PWM. Therefore, the averagevoltage E₁ is changed by the PWM control and the speed of the motor 105is controlled by the inverter 104.

Thus, the voltage which is applied to the motor 105 is set to the samevoltage in both cases where the AC power source 101 is of the lowvoltage system and where it is of the high voltage system. One kind ofbrushless DC motor 105 can be used irrespective of the power sourcevoltage 116.

An operating apparatus of FIG. 38 differs from that of FIG. 31 withrespect to a point that the decision regarding whether the AC powersource voltage 116 is of the low voltage system or of the high voltagesystem is performed on the basis of the output voltage of the rectifier102. Since the output signal 130 of the DC voltage comparing section 125has a pulse waveform, a latch circuit 125c is provided an output of thelatch circuit 125c is input to the microcomputer 106. With thisconstitution, by fetching this output signal, it is always possible todetermined whether the power source voltage E_(d) is of the low voltagesystem or of the high voltage system.

We claim:
 1. An apparatus for operating a vacuum cleaner comprising:aspeed control unit having a brushless DC motor and an inverter controlunit to drive said brushless DC motor for use in a vacuum cleaner;wherein said inverter control unit comprises a control circuit whichincludes a microcomputer, a current detecting circuit for detecting loadcurrent of the motor, a magnetic pole position detecting circuit fordetecting the rotating position of the motor, and a speed commandcircuit for producing a speed command; said microcomputer includingmeans for calculating a load state of the cleaner from a load currentand a rotational speed of said brushless DC motor, means for controllingmotor speed by controlling a voltage or a current which is applied tothe brushless DC motor in response to said speed command, and means forcorrecting said speed command on the basis of the calculated load stateso that the brushless DC motor exhibits a series wound characteristic.2. An apparatus according to claim 1, wherein the speed of saidbrushless DC motor is controlled by said microcomputer in an activationmode in which speed is detected and controlled according to said speedcommand, and thereafter in a series wound control mode in which speed iscontrolled using a speed command which is obtained by correcting saidspeed command produced by said speed command circuit on the basis ofsaid calculated load state.
 3. A vacuum cleaner, comprising:a housinghaving an air flow inlet, an air flow outlet and an air passageextending between said air flow inlet and said air flow outlet; a filterin said air passage to collect particles in air flowing in said passage;a fan driven by a brushless DC motor for producing an air flow in saidair flow passage; a speed command circuit for producing a speed command;means for determining the rotational speed of said brushless DC motor;means for detecting the load current of said brushless DC motor; meansor calculating the load state of said cleaner from the rotational speedand the load current of said brushless DC motor; means for controllingmotor speed by controlling a voltage or current which is applied to saidbrushless DC motor in response to said speed command; and means foradjusting said speed command in accordance with said calculated loadstate to cause said brushless DC motor to exhibit a series woundcharacteristic.
 4. A vacuum cleaner according to claim 3, wherein saidcontrolling means includes means responsive to said speed command forcontrolling the speed of said brushless DC motor on the basis of thedetermined rotational speed thereof until a speed indicated by saidspeed command is reached, and thereafter for controlling the speed ofsaid brushless DC motor by adjusting said speed command on the basis ofthe calculated load state to operate the brushless DC motor with aseries wound characteristic.
 5. A vacuum cleaner, comprising:a filter tocollect particles from a surface to be cleaned; a brushless DC motorconnected to a device to cause particles to be picked up from saidsurface and collected by said filter; a speed command circuit forproducing a speed command; means for determining the rotational speed ofsaid brushless DC motor; means for detecting the load current of saidbrushless DC motor; means for calculating the load state of said cleanerfrom the rotational speed and the load current of said brushless DCmotor; means for controlling motor speed by controlling a voltage orcurrent which is applied to said brushless DC motor in response to saidspeed command; and means for adjusting said speed command in accordancewith said calculated load state to cause said brushless DC motor toexhibit a series wound characteristic.
 6. A vacuum cleaner according toclaim 5, wherein said controlling means includes means responsive tosaid speed command for controlling the speed of said brushless DC motoron the basis of the determined rotational speed thereof until a speedindicated by said speed command is reached, and thereafter forcontrolling the speed of said brushless DC motor by adjusting said speedcommand on the basis of the calculated load state to operate thebrushless DC motor with a series wound characteristic.
 7. An apparatusfor operating a vacuum cleaner, comprising:a brushless DC motor; meansfor producing a speed command; means for determining the rotationalspeed of said brushless DC motor; means for detecting the load currentof said brushless DC motor; means for calculating the load state of saidcleaner from the rotational speed and the load current of said brushlessDC motor; means for controlling motor speed by controlling a voltage orcurrent which is applied to said brushless DC motor in response to saidspeed command; and means for adjusting said speed command in accordancewith said calculated load state to cause said brushless DC motor toexhibit a series wound characteristic.
 8. An apparatus according toclaim 7, wherein said controlling means includes means responsive tosaid speed command for controlling the speed of said brushless DC motoron the basis of the determined rotational speed thereof until a speedindicated by said speed command is reached, and thereafter forcontrolling the speed of said brushless DC motor by adjusting said speedcommand on the basis of the calculated load state to operate thebrushless DC motor with a series wound characteristic.